Method and apparatus for recording vectorcardiographs



April 12, 1960 N. G. KLING Erm. 2,932,549

METHOD AND APPARATUS FOR RECORDING VECTORCARDIOGRAPHS Filed Nov. 20, 1953 MQDFL ATTORNEYS States Nelson G. Kung, Roslyn, :ma Milam H. Pelavin, Brooklyn, N.Y., assignors, by mesne assignments, to Technicon instruments Corporation, Chauncey, N.Y.

Application November 20, 1953, Serial No. 393,312

9 Claims. (Cl. Seis-110) Our invention relates to a method and apparatus for automatically recording transient phenomena, and more speciically to the recording of a vector summation of two simultaneous signals from such phenomena.

The making of photographic recordings of Lissajous ligure traces formed on the screen of a cathode ray oscilloscope has presented a problem due to the superimposition of the recorded traces where the traces result from signal voltages which, though repetitive are nonidentical. In making such a recording, the photographic lm is subjected to the spot of -light formed by the beam of electrons on the screen of the oscilloscope, the path of the rapidly moving light spot forming a dgure trace, although at any given instant during the formation of the ligure trace, the electron beam produces only a single light spot on the screen, the location of which is determined by the relationship of the signal voltages at that particular instant. Thus in the formation of a Lissajous figure, for example, a circle, what actually is happening is that a spot of light is moving at an extremely rapid rate in a circular path, the spot eventually returning to the starting point in order to complete the circular loop path. Thus, in order to take a picture of the complete trace, the film must be exposed lduring the entire movement of the beam of `light in forming the complete trace.

Now, if a horizontal sweep voltage be applied during the formation of a circular Lissajous ligure, in order to moveV the electron beam across the screen so that a succeeding trace, as recorded on the lm, will not be superimposed upon a prior trace, as recorded thereon, it will be apparent that by the time the spot of light or the electron beam is to return to its starting point to complete the circular trace, the electron beam will have moved horizontally relative to its starting point, and thus the loop path will fail to close and the result will be a distorted trace rather than a true reproduction on the lilm of the resultant of the combined signal voltages. While a circular Lissajous ligure is illustrated and described herein, in order to facilitate the description of the present invention, it will be understood, however, that in practice, Lissajous iig-tires are extremely complex. For example, in the art of cardiology, a vectorcardiogram trace is a Lissajous tigure, and reference is made to Spatial Vectorcardiography, by Grishman and Scherlis, published by W. B. Sanders Company, Philadelphia and London, 1952, for illustrations of actual vectorcardiogram traces. Since the above mentioned distortion is a direct result of the additional voltage supplied to the horizontal deflection plates by the horizontal sweep means, neutralization of this additional voltage or horizontal component will eliminate said distortion. Thus, the basic concept of our present invention is to move a sensitized lilm, onto which the moving light spot is focused, in cor-relation with the rate of movement of the light spot across the screen of the oscilloscope so that the movement of the tllm will compensate for the horizontal movement of the trace formed by the light spot. Consequently, even though the path of movement of the atelight spot on the screen of the oscilloscope will form or determine an incomplete and distorted Lissajous igure, the film will actually record the true, undistorted Lissajous figure representative of the signal voltages.

,Y Therefore, in accordance with the foregoing, the primary object of the present invention is the provision of means for obtaining true or faithful reproductions of successive resultants of separate signal voltages which resultants are non-identical and repetitive in character.

Another object of the invention is the provision of a method of and apparatus for photographically recording transient phenomena. In this connection, a more specific object of our invention is to provide a method and apparatus for the automatic photographic recording of a trace appearing on a cathode ray oscilloscope, which trace is the resultant of simultaneous signals supplied to the oscoilloscope by the transient phenomena under investigation.

Another object of our invention is the provision of automatic photographic recording means having a continuously moving lm, and means for correlating the movement of the iilm with the movement ofthe electron beam across the screen of an oscilloscope.

Another object of our invention is the provision of an automatic photographic recording method and apparatus which is especially advantageous in recording varying vectors, for example, vectorcardiograms, as well as other biological voltages, and which is also useful for other purposes.

The above and other objects, features and advantages of the invention will be fully understood from the following description considered With reference to the accompanying illustrative drawings.

In the drawings, which illustrate the best mode pres ently contemplated by us of carrying out our invention:

Fig. l is a more or less diagrammatic and schematic representation of the preferred form of our invention;

Fig. 2 is a schematic View of a variable resistor connected to the potentiometer employed in the preferred form of our invention; and

Fig. 3 is a more or less diagrammatic and schematic representation of a modified form of our invention.

Because of the utility of the invention in the art of cardiology, and also for the sake of convenience and to facilitate the description thereof, our invention has been illustrated and will de described in connection with its application to the field of cardiology, and more specilically, to vectorcardiography. However, while the use of our invention in vectorcardiography constitutes an application of primary importance, it is to be understood that the basic concept thereof can be applied to the recording of various other transient phenomena such as, for example, but without limitation, various biological voltages, the monitoring of line voltages, phase shifts, etc. By transient phenomena, reference is made to phenomena that emit re-occurring but non-identical signals.

In the practice of vectorcardiology, the resultant of two simultaneous voltages across different parts, respectively, ofthe subjects body is observed. For example, in taking a vectorcardiograph in the so-called frontal plane, one pair of electrodes may be applied to the patients left arm and left leg and another pair may be applied to the patients left arm and right arm. The two voltages thus obtained may then be supplied to a cathode ray oscilloscope, after being suitably amplified. For example, the left arm-left leg may be supplied to the vertical dellecting plates of the oscilloscope while the left arm-right arm may be supplied to the horizontal dellecting plates. When the two voltages thus obtained are out of phase, the resulting trace on the scope will be in the form of a closed loop, known in the art as a Lissajous ligure,

which will represent a vector sum of the aforelisted components, but it is to be emphasized that this is an instantaneous vector and represents the resultant of the forces of the heart measured for only one cardiac cycle. Since the forces of the heart for each cardiac cycle are dierent, it follows that the vector for each cardiac cycle will be different as well, this being an example of transient phenomena. The problem which presents itself is that of recording this constantly changing vector as it is presented on the oscilloscope, and it is this problem with which the present invention deals.

Referring now to the drawings, and more particularly to Fig. 1 which represents the preferred form of our in'- vention, reference numeral generally designates a cathode ray oscilloscope having vertical-deflecting plates 12 and horizontal-deflecting plates 14. The electrode applied,.for example, to the subjects left arm, designated atYLA and the electrode applied to the left leg of the subject and designated at LL supply a signal voltage to vthe vertical-deliecting plates 12 of the cathode ray oscilloscope, which voltage represents the vertical component of the vector being obtained. Before being applied to the vertical deflecting plates 12 this voltage is amplified by an amplifier 15 from which it is fed to the verticaldeection amplifier 16 of the oscilloscope. The horizontal component represents, for example, a voltage across the left arm LA of the subject and the right arm of the subject, designated at RA, which is -applied as a signal voltage to the horizontal-deecting plates 14 of the cathode ray oscilloscope. Before reaching the horizontal-deflecting plates, this signal voltage is amplified by amplifier 17, and fed through resistors 19 and 21, for reasons to be later set forth, to the horizontal-defiection amplifier 18, of the oscilloscope. It will be understood that since both pairs of electrodes are in contact with the subject, both the horizontal signal voltage and the vertical signal voltage are transmitted simultaneously from the subject to the cathode ray oscilloscope. It will -further be understood that the trace formed on the cathode ray tube, as the result of the simultaneous horizontal and vertical signals being supplied thereto, will represent a vector or resultant of said horizontal and vertical signals, as is well known to those skilled in the art.

The means for automatically recording the above described transient phenomena will now be described. Photographic means comprising a spherical convex objective lens assembly 22 and a continuously moving sensitized film 24, positioned therebehind, are provided. The basic concept of the instant invention is to continuously drive the film 24 so that the linear rate of travel of the film is the same as the linear rate of rtravel of the light spot image, as focused thereon. With a magnification ratio of 1:1 for the lens assembly 22, the film is moved at precisely the same speed as the rate of linear travel of the light spot across the oscillosope screen. With a magnification ratio other than lx1, suitable compensation is made in the rate of linear travel of the film to provide that the image of the light spot, as focused thereon, is moved at the same linear rate as the film. If this relation between the linear movement of the film 24 and the linear movement of the image focused thereon is accurately maintained, a complete and undistorted photographic recording of the trace will be obtained. On the other hand, if this relationship is not accurately maintained, the resulting picture of the tract will be blurred and distorted. Thus it is highly desirable to eliminate relative linear movement between the image as projected on film 24 and the film. The manner in which this is accomplished pursuant to out invention, will now be described.

The film 24 is driven by a synchronous motor 26 having suitable reduction gearing, generally indicated at 28, for driving shaft 34 which has fixedly mounted thereon a film feed roller 36. The film 24 is fed from a supply roll or spool 38 rotatably mounted on spindle 40 and is directed over guide roller 42, rotatably mounted on shaft 44, and continues across the front of the oscilloscope screen and the objective lens assembly 22 to the feed roller 36 and then on to cassette 46. A pressure roller 48 is urged by spring 50 against the film in engagement with feed rollerV 36 thereby insuring that the film makes sufficient frictional contact with said feed roller so as to be driven thereby. It will be understood that a drag may be applied to the feed roll 38 by any suitable means (not shown) in order to prevent overrunning of the film thereby maintaining the film taut during its travel to the feed roller. Cassette 46 is an open top cylindrical enclosure having an elongated cut-out portion 52 disposed vertically on its side surface and receiving the film therein. A suitable fiat spring 54 may be disposed within the cassette to insure proper rerolling of the film. The arm or tap 58 of a potentiometer, designated generally at 56, is mounted near the lower end of shaft 34 and is utilized to provide a horizontal sweep voltage for the horizontal-deflection plates 14 of the cathode ray oscilloscope. As here shown, the potentiometer terminals 59 and 61 are connected to the terminals of battery supply 63, terminal 59 being connected by lead 67 to the horizontal deflection amplifier 18, and tap 58 being connected thereto by lead 65. The resistors 19 and 21 serve to isolate the sweep voltage and the body voltage from the LA-RA electrodes so as to provide for the proper addition of the voltages in the horizontal defiection amplifier to assure the amplification of the additive total thereof by said amplifier. The potentiometer arm 58 being secured to the lower end of shaft 34 for rotation therewith, it will be seen that the speed of shaft 34 directly controls the sweep voltage supplied by the potentiometer to the horizontal deflecting plates 14. As arm 58 is rotated by the shaft 34 from terminal 59 to terminal 61 a sweep voltage cycle will be supplied to the horizontal defiecting plates 14, the sweep voltage cycle terminating when the arm travels from terminal 61 to terminal 59 to again initiate the sweep voltage signal when the arm again contacts the terminal 59. The potentiometer 56 is connected to the oscilloscope in place of the horizontal sweep generator usually employed in an oscilloscope for regulating the horizontal linear movement of the trace across the oscilloscope, and it will be understood that said sweep generator is not used. Since, as described, the potentiometer tap is directly coupled to the shaft 34 which controls the feed of the film, it will be obvious that the linear rate at which the trace moves across the scope can be correlated with the rate at which the film is fed so that the image, as projected on the film, will move at the same rate as the film. This arrangement is particularly advantageous because of the fact that any unforeseen variations in the film feed will result in corresponding variations in the movement of the trace across the scope. The maximum voltage supplied to the horizontal-deflecting plates 14 by potentiometer 56 will determine the limits of the travel of trace 20 across the scope. Accordingly, if it be desired to vary the limits of linear movement of said trace, a variable resistor 60 may be coupled in series with the potentiometer as shown in Fig. 2 thereby varying the maximum voltage supplied thereby. More specifically, the rheostat 60 is connected in series with the battery supply 63, and with the potentiometer 56. Consequently, the setting of tap 69 of rheostat 60 will determine the distance of linear travel of the trace 20 across the screen of the oscilloscope. It may also be desirable to vary the speed at which film 24 is fed in order to adjust for the frequency or rate of heartbeats in different patients. This is important since, where a subject has a rapid heart beat, relatively slow f eed of the film and correspondingly slow movement of the trace could conceivably result in superimposition of succeeding traces on the film. This variation in speed may be vobtained by changing the reduction gears 28 although it -will be understood, of course, that any suitable variable speed transmission may be used.

As is well known to those skilled in the art, the sweep voltage which is ordinarily applied to the horizontal deilection plates also provides a time base which can be utilized for determining the time required to complete a trace formed on the screen of the oscilloscope by a signal applied to the vertical deiiection plates. However, since in the present invention a signal voltage is additionally provided on the horizontal deection plates to form a Lissajous ligure, some other timing means must be provided for determining the time required to form the complete trace. For this purpose, provision may be made for intensity modulation of the control grid 71 of the cathode ray tube with a signal of predetermined frequency from a suitable intensity modulator of known type, such as indicated at 73, the output of which is developed across a control grid bias resistor 75 between control grid 71 and the cathode 77 which is connected to a negative high voltage (-H.V.) source, as is well known to those skilled in the art. When a sine wave signal is used for intensity modulation of the control grid, the time required to form the complete trace may be readily determined by counting the number of high intensity portions of the trace and comparing said number with the known frequency of the modulated signal. Under certain circumstances, it may be desirable to determine the general direction of movement of the electron beam in forming the trace, for example, whether the beam is moving generally clockwise or generally counterclockwise during the formation of a Lissajous figure. In this connection, an intensity modulator which provides a saw tooth voltage may be used, in lieu of the sine wave voltage, and the high intensity portions of the trace will then have a generally tear drop outline, the beam traveling in the direction from the substantially pointed narrow end of the tear drop to the Wider arcuate end thereof.

The operation of the above described apparatus for practicing our method is thought to be obvious from the foregoing, but a brief summary thereof will now be given. By supplying the vertical signal to the vertical-deiiecting plates i2 of the cathode ray oscilloscope and by supplying the horizontal signal to the horizontal deiiecting plates 14, a resultant trace will be formed which trace represents the vector of the two signals being supplied simultaneously to the oscilloscope. A sweep voltage is additionally supplied to the horizontal plates 14 for effecting the linear movement of the trace horizontally across the screen. This sweep voltage is developed by potentiometer 56 which in turn is controlled by the speed of shaft 34. Thus, a direct relation is established between the linear movement of the trace across the screen and the speed of shaft 34, which, of course, controls the rate of feed of the film 24. It will be understood that successive images, on the lm, indicated at a and Zlib, of the traces as they appear in succession on the screen of the oscilloscope will be spaced from each other longitudinally of the lm according to the distance of the horizontal travel of the individual traces on the screen of the oscilloscope, subject to any magnication by lens 22. Although other means could be employed for moving the lm 24 in correlation with the linear movement of trace 20' across the screen, as regulated by a conventional horizontal sweep generator, the method herein described is highly desirable because it obviates the possibility of linear movement of the film and trace image, as projector thereon, in relation to each other which might otherwise occur under circumstances which cause a variation in speed of the film, so that said film feed would no longer retain its proper relation with respect to the rate of the linear movement of the trace. in the instant invention, however, since there is a tie-in between the rate of film freed and the linear movement of the trace any variations inthe former will automatically be compensated for and 6 the proper relationship will at all times be maintained, and a clear, undistorted image will be recorded.

Fig. 3 represents a modified form of our invention which will now be described. The basic concept of this form is similar to that of my preferred embodiment in that the speed of the lm feed is related to the linear movement of the trace across the screen of the oscilloscope. Instead of having the film feed regulate the linear movement of the trace, however, the movement of the film is controlled in accordance with said linear movement. This is accomplished in the following manner. The horizontal and vertical signals are supplied to horizontal and vertical deflection amplifiers 62 and 64, respectively, and then to the horizontal and vertical deflection plates 65 and 68, respectively, of cathode ray oscilloscope 7) in a manner identical to that described in connection with my preferred embodiment. Horizontal linear movement o f the resultant trace is elected by sweep generator 72 in a conventional manner. The sweep generator is additionally connected to a power oscillator 74 to operate the latter in synchronism with the rate of horizontal deflection of the trace, the oscillator providing a signal output of higher frequency than the sweep generator. The oscillator output signal is amplifred by power amplier 76 and then multiplied by the frequency multiplier Sil to a frequency level required for efficient operation of the motor 78 which requires voltage of a much higher frequency than that provided by the sweep generator 72. Suitable reduction gearing, as at 82, is then provided so that the shaft 34 may be driven by the motor 78 at the rate required for movement of the lm in correlation with the linear movement of the trace across the screen. The film mounting and feed means are identical to that described in the preferred embodiment and accordingly no further description pertaining thereto will be given. It will be understood, however, that the potentiometer employed in the preferred embodiment is not utilized in the modification, just as the sweep generator of the modified form is not utilized in the preferred form. lt will be further understood that the intensity modulating means, as previously described in connection with the preferred embodiment, may be similarly utilized in connection with the present embodiment.

Therefore, it will be apparent from the foregoing that although the frequency of the sweep generator output may be quite low, for example, and not by way of limitation, sixty cycles per minute, it vcan Abe used to drive a high speed motor, for example, and not by way of limitation, a motor operating in a range from 1809-3000 rpm. to provide desired efficiency, and then reduce the frequency of the motor output to drive a film feed effrciently and in synchronism or in correlation with the movement of the trace across the screen.

From the foregoing, it will be apparent, that in the constructions illustrated in Figs. l and 3, and utilizing sign-al voltages which, for example would normally from a circular trace in the absence of a sweep voltage, the light beam follows a non-circular path, as illustrated at 2u, in Fig. l, due to the fact that the electron beam is subjected to the horizontal sweep voltage. However, the continuous horizontal movement of the hn 24; neutralizes the effect of the horizontal sweep voltage so that the trace which is recorded on the film is a circular trace, `as illustrated at 20a. In this connection it will be understood that since the lens `22. is a reversing lens, the movement of the film from the supply roll 38 to the cassette 46 is in a direction opposite to the direction of the horizontal deflection of the electron beam by the sweep voltage. While 26a illustrates a completely recorded trace, Ztlb illustrates a partially recorded trace, it being understood that trace 2Gb will form a complete circle when the electron beam has completed a trace 2u.

lt will be understood also that, in the movement of the iihn at a uniform speed -in front of the screen of the oscilloscope, the film is continuously exposed in succes- 7 sion to the light` of each of the traces while each trace is being formed on said screen, and in this connection it will be understood further that no shutter is required in view of the continuous exposure of the film to the traceforming light on the screen pursuant to the present invention.

Although the present invention is primarily and especially useful and beneficial in the automatic recording of vectors or Lissajous figures of transient phenomena, it can be utilized also in connection with ordinary electrocardiographs or other phenomena wherein one signal of varying amplitude is recorded with respect to time or some other variable. Pursuant to the accomplishment of this function, the potentiometer of -my preferred embodiment is disconnected and no sweep signal at all is supplied to the horizontal deiiecting plates. A signal voltage from the electrodes attached to the patient will be supplied to the vertical-deecting plates and will be recorded on the horizontally moving film 24, the movement of the film, in effect, serving the same function as a sweep voltage. Consequently, as to this aspect of the invention both the sweep generator and the horizontal deecting plates may be omitted from the oscilloscope.

It will be understood that the film and its supply and take-up devices are arranged in a suitable cabinet or housing (not shown) so as to exclude all light except that of the trace on the `oscilloscope screen; alternatively, the apparatus may be disposed in a dark room.

While we have shown and described the preferred embodiments of our invention, it will be understood that various changes may be made in the idea or principles of the invention within the scope of the' appended claims.

Having thus described our invention, what we claim and desire to secure by Letters Patent is:

l. Apparatus of the character described comprising an oscilloscope provided with a screen and pairs of horizontal and vertical deecting plates, means for simultaneously applying first and second repetitive signal voltages to the horizontal and vertical deecting plates, respectively, of said oscilloscope whereby to `form a selies of traces in succession on said screen of said oscilloscope, sweep means connected to one of said pairs of deflecting plates for effecting movement of said traces during formation thereof, whereby to prevent successive tnaces on the screen from overlapping or being superimposed on each other, continuously moving recording means sensitive to said traces and disposed in operative relation to said screen, means for moving said recording means in a direction such that the direction of movement of the recorded image is opposite to the direction of trace movement on said screen, and means for synchronizing the rate of movement of said recording means with the rate of movement of said traces, said recording means being moved parallel to the movement of said traces and in synchronization therewith to form undistorted reproductions of said traces.

2. Apparatus of the character described comprising an oscilloscope provided with a screen and pairs of horizontal and `vertical deflecting plates, means for simultaneously applying first yand second repetitive signal voltages to the horizontal and vertical deflecting plates, respectively, of said oscilloscope whereby to form a series of traces in succession on said screen of said oscilloscope, sweep means connected to one of said pairs of deliecting plates for effecting movement of said traces during formation thereof, photographic means for recording said traces individually in succession as they are formed on said screen, said photographic means being positioned in operative relation to said screen `and having a continuously moving film, means for moving said recording means in a direction such that the direction of movement of the recorded image is opposite to the direction of trace movement on said screen, and means for synchronizing the rate of movement of said film with the rate of movement of said traces, the movement of said film being parallel to the movement of said traces and in synchronization therewith to form undistorted reproductions of said traces on said film.

3. Apparatus of the character described comprising an oscilloscope provided with a screen and pairs of horizontal and vertical deecting plates, means for simultaneously supplying first and second out of phase signal voltages to the horizontal and vertical deflection plates, respectively of said oscilloscope, so as to form a series of non-identical traces on said screen of said oscilloscope, sweep means for effecting movement of said traces during formation thereof, photographic means for continuously recording said traces, said photographic means being positioned in operative relation to said screen and having a continuously moving film, drive means for feeding said film in a direction such that the direction of movement of the recorded image is opposite to the direction of trace movement on said screen, and means for operating said sweep means at a rate governed by the rate of operation of said drive means whereby the rate of feed of the film may be synchronized with the rate of movement of the traces across the screen of the oscilloscope, the movement of said traces being parallel to the movement of said film and in synchronization therewith to form undistorted reproductions of said traces on said film.

4. Apparatus of the character described comprising an oscilloscope provided with a screen and pairs of horizontal and vertical deflecting plates, means for simultaneously applying first and second out of phase signal voltages to the horizontal and vertical defiecting plates, respectively, of said oscilloscope, so as to form a series of non-identical traces on said screen of said oscilloscope, sweep means for effecting movement of said traces during formation thereof, photographic means for continuously recording said traces, said photographic means being positioned in operative relation to said screen and having a continulously moving film, drive means for feeding said film in la direction such that the direction of movement of the recorded image is opposite to the direction of trace movement on said screen, and means for operating said drive means at a rate governed by the rate of operation for said sweep means whereby the movement of the traces across the screen of the oscilloscope may be synchronized with the rate of feed of the film, the movement of said film being parallel to the movement of said traces and in synchronization therewith to form undistorted reproduction of said traces on said film.

5. Apparatus of the character described comprising an oscilloscope provided with a screen and pairs of horizontal and vertical detlecting plates, means for simultaneously applying first and second out of phase signal voltages to the horizontal and vertical deflecting plates, respectively, of said oscilloscope, so as to form a series of nonidentical traces on said screen of said oscilloscope, sweep means for effecting movement of said traces during formation thereof, photographic means for continuously recording said traces, said photographic means being positioned in operative relation to said screen and having a continuously moving film, drive means for moving said film in a direction such that the direction of movement of the recorded image is opposite to the direction of trace movement on said screen, said drive means comprising a driven shaft and a feed roller operated thereby, and means for operating said sweep means at a rate governed by the rate of operation of said shaft whereby the rate `of feed of the film may be synchronized with the rate of movement of the traces across the screen of the oscilloscope, the movement of said traces being parallel to the movement of said film and in synchronization therewith to form undistorted reproductions of said traces on said film.

6. Apparatus of the character described comprising an oscilloscope provided with a screen and pairs of horizontal and vertical deecting plates, means for simultaneousi ly applying first and second out of phase signal voltages `iilm in a direction such that the direction of movement of the recorded image is opposite to the direction of trace movement on said screen, said drive means comprising a driven shaft, a feed roller operated by said sha-ft, a motor for driving said shaft, and means responsive to the rate of operation of said sweep means for controlling the speed of said motor whereby the rate of movement of the traces -across screen of said oscilloscope may be synchronized with the rate of feed of the film, the movement of said iilm `being parallel to the movement of said traces.

7 Apparatus for taking vectorcardiographs comprising an oscilloscope provided with a screen and pairs of horizontal and `vertical deliecting plates, means for simultaneously applying a iirst Iand a second body voltage to the horizontal and vertical dellecting plates, respectively, of said oscilloscope whereby to -form a series of traces in succession on said screenof'said oscilloscope, photographic means `for recording said traces individually in succession as they are formed on the screen comprising a movable film, feed means for moving said lm in a direction such that `the direction of movement of the recorded image is opposite to the direction of trace movement on said screen, said drive means comprising a driven shaft, a feed roller operated by said shaft, a potentiometer n circuit with one of the pairs of deecting plates` in said oscilloscope so as to apply a sweep voltage thereto, the arm of said potentiometer being secured to said driven shaft for rotation therewith whereby the rate of operation of said feed means controls the rate of movement of said vtrace kacross the screen of the oscilloscope, the movement of said traces being parallel to the movement of said iilm and in synchronization therewith to form undistorted reproductions of said traces on said lm.

8. Apparatus of the character described comprising a cathode ray tube having ia screen, vertical deilecting means and horizontal deecting means, means to apply frst signal voltages to said vertical deilecting means and means to apply second signal voltages to said horizont-a1 deilecting means to form a series of successive gure traces on said screen, means to -generate sweep voltages and to -apply said sweep yvoltages to one of said delecting means during the formation of said figure traces with the other of said dellecting means being free of sweep voltages, whereby each gure trace is moved over said screen during the formation thereof to clear the screen for the formation of the next succeeding trace, and means to move a sensitized Ifilm past said screen parallel to the movement or" said traces in a direction such that the dilrection of movement of the recorded image on said lm is opposite to the direction of trace movement on said screen and at a rate in synchronism with the rate of said movement of the figure traces to form undistorted reproductions of said iigure traces on said iilm.

9. Apparatus for recording vectorcardiographs comprising an oscilloscope having a screen and a pair of horizontal beam deecting plates and a pair of vertical beam deflecting plates, means for simultaneously applying a irst and a second body voltage to said horizontal and vertical deiiecting plates, respectively, of said oscilloscope so as to form a ser-ies of traces in succession on `said screen of said oscilloscope, sweep means connected to said pair of horizontal deiiecting plates for effecting horizontal movement of said traces over said screen during the formation thereof, photographic means for recording said traces individually in succession as they are formed on said screen, said photographic means being positioned in operative relation to said screen and having a continuous sensitive iilm moving horizontally and parallel to the horizontal movement of said traces, means 'for moving said lfilm in a direction such that the direction of movement of the recorded image is opposite to the direction of trace movement on said screen and means for synchronizing the rate of movement of said lm with the rate of movement of said traces so as to form undistorted reproductions of said traces on said film.

References Citedin the file of this patent UNITED STATES PATENTS 1,907,549 Kahrs May 9, 1933 2,098,695 Southwick Nov. 9, 1937 2,214,299 Heller Sept. l0, 1940 2,241,432 Ardenne et al. May 13, 1941 2,275,898 Goldsmith Mar. 10, 1942 2,425,003 Potter Aug. 5, 1947 2,430,283 Epstein Nov. 4, 1947 2,458,291 Munster et al. Ian. 4, 1949 2,489,253 Andre Nov. 29, 1949 2,596,741 Tyler et al. May 13, 1952 2,603,775 Chipp July 15, 1952 2,605,162 Gantt July 29, 1952 2,628,881 Adams Feb. 17, 11953 2,659,363 Brosselin Nov. 17, 3 2,702,158 Winter Feb. 5, 1955 2,726,919 Hathaway et al. Dec. 13, 1955 2,735,956 McNaney IFeb. 21, 1956 

